3o6 THR PLACr: OF MIMICRY 



It has been contended b) Mr, W. liateson ^ that there 

 is no strucfij^le for existence diirini^ the pupal stage of 

 Vafiessii nr/icac (the Small Tortoiseshell Huttertly), and 

 that, therefore, its power of colour-adjustment is not 

 related to any danger, and cannot have been evolved by 

 Natural Selection. An attempt has been made by Miss 

 C. H. Sanders. Miss M. K. Notley. Miss F. A. Wright, 

 and the author to test this conclusion b\- exposing the 

 pupae of itr/icae :ind allied species upon environments of 

 various kinds, and keeping a careful watch upon them. 

 The results, of which onl)- a preliminary statement has 

 been published." prove that there is immense destruction 

 during the pupal period, short as it is, and that these 

 anovular chrysalises fixed to fiat surfaces were in far 

 greater danger than when suspended against a rough 

 background. On the other hand, the evidence of pro- 

 tection afforded by colour-harmon) with the environment 

 was far less clear in these experiments. 



The power of individual colour adaptation known to 

 exist in many larvae and exposed pupae of Lepidoptera 

 received a striking and novel illustration in some experi- 

 ments conducted at Oxford in iS9'^-4.^ The larvae of 

 the Geometrid moth Odontopcra bidcntata were found 

 to be extremely sensitive to the various shades of brown 

 and grey, colouring the bark of their natural food-plants. 

 The green of the leaves, on the other hand, did not 

 produce green but extremely pale brown caterpillars. 

 It is to be noted, furthermore, that th(! larvae do not 

 rest on the leaves by day, but only on the twigs and 

 branches. So far, the experiment was conducted along 

 the same lines as the earlier investigations, and yielded 

 similar results. The exposure of the larvae to lichen- 

 covered branches produced effects unseen in previous 

 experiments, vi/., brown, bark-like larvae, bearing green, 

 lichen-like markings. The contrast between the effect ofj 

 the continuous green surfaces of the leaves and the scat- 

 tered green of the lichen was remarkable and striking. 



* Trans. Ent. Soc., LofuL, 1892, pp. 2:2-13. 



^ Report 0/ the British Association, Bristol IMeeting, 1898, pp. 906-9. 



' Fully described in Trans. Ent. Soc, Land., 1903. p. 311, plates 



xvi-xviii. 



I 



